I am about to change from a 351M in my 76 F250 4x4, to a 300 I6. My initial impression was that I would need new mount towers. But since I started asking around for some, I've been told that all I had to do was move my current towers up to the "next set of pre-drilled holes", and I've also been told that the towers stay the same, and that it's just the mounts themselves that make up the obvious difference in width between the V8 and the I6.

Can someone maybe clear up the confusion for me? How must I take the fact that my truck is a highboy (frame width) into account??

Any help is much appreciated, as I'm itchin to get this rattley old modified out of my truck. (for now at least).

 

I have done a 6cl to 302 swap and i had to change the towers.. just to be safe i would change them.. Look at the truck the 300 is comeing out of to see what holes to use.. i just got one question why go from a v8 to a 6cl??

 

it's more a matter of economics. I'm a university student on a limited budget. I happen to have a 300 six kicking around, and will use it while I take my time finding the right engine for my truck, or rebuilding the modified if it's worth it.. its not rattling too bad.....yet......

actually, a 300 six in front of a np435 "farm four" and driving 4.10 gears doesnt sound bad to me.. the I6 has to put out about the same tourque as my tired 351M

i wont know until i try it!

 

300 and 351m frame brackets are different. My 79 F150 originaly had 351m, someone swapped to 300 using 351m brackets moved forward to 300 position and torched new holes so rubber mounts would fit. The engine was to low in chassis and crushed the oil pan. I think F150 and F250 frames are the same width in motor mount area. Mine is 26 1/4 " between frame rails where the mounts bolt on, 33 1/2" outside.

 

that information is usefull... if memory serves me well, my frame is 34 outide to outside.. hmmmmmmmmmmmmm



thank you!

 

From the rear cab mount forward all frames are the same width.

FWIW I took a 300 6 out of my '78 F250 4x4 and put it in my '76 F 150 4x2 that had a 360 in it. All I did was move the frame mounts forward. The frame mounts should be the same. The motor mount on the left side of the motor is longer to compensate for the offset block. If you look at a 300 6 you see what I am talking about. The same reason why you can't interchange the inline and V motor fan shrouds.

ecarter50, you must have had the wrong oil pan (front sump) on the motor becouse the 300 6 mounts way down in the frame like the 351/400. Also, I'm not sure why any torching would be needed, the only motor that didn't use the stud type mount was the 460.

 

now thats what i was after. you have confirmed information that I've heard elsewhere, but i didnt completely trust that source.

the source is right on some things, wrong on others. I also thought the frames were the same width up front, just that the non-1 ton or highboy trucks frames spread apart behind the cab, whereas the 1 ton / highboy frames stay the same width.

now i am ready to tear this truck apart.. thank you!